Systems and methods for aluminum-containing film removal

ABSTRACT

Exemplary etching methods may include flowing a halogen-containing precursor into a substrate processing region of a semiconductor processing chamber. The halogen-containing precursor may be characterized by a gas density greater than or about 5 g/L. The methods may include contacting a substrate housed in the substrate processing region with the halogen-containing precursor. The substrate may define an exposed region of an aluminum-containing material. The contacting may produce an aluminum halide material. The methods may include flowing an etchant precursor into the substrate processing region. The methods may include contacting the aluminum halide material with the etchant precursor. The methods may include removing the aluminum halide material.

TECHNICAL FIELD

The present technology relates to semiconductor processes and equipment.More specifically, the present technology relates to selectively etchingaluminum-containing structures.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers, or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess that etches one material faster than another facilitating, forexample, a pattern transfer process. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits, and processes, etch processes have been developedwith a selectivity towards a variety of materials.

Etch processes may be termed wet or dry based on the materials used inthe process. For example, a wet etch may preferentially remove someoxide dielectrics over other dielectrics and materials. However, wetprocesses may have difficulty penetrating some constrained trenches andalso may sometimes deform the remaining material. Dry etches produced inlocal plasmas formed within the substrate processing region canpenetrate more constrained trenches and exhibit less deformation ofdelicate remaining structures. However, local plasmas may damage thesubstrate through the production of electric arcs as they discharge.

Thus, there is a need for improved systems and methods that can be usedto produce high quality devices and structures. These and other needsare addressed by the present technology.

SUMMARY

Exemplary etching methods may include flowing a halogen-containingprecursor into a substrate processing region of a semiconductorprocessing chamber. The halogen-containing precursor may becharacterized by a gas density greater than or about 5 g/L. The methodsmay include contacting a substrate housed in the substrate processingregion with the halogen-containing precursor. The substrate may definean exposed region of an aluminum-containing material. The contacting mayproduce an aluminum halide material. The methods may include flowing anetchant precursor into the substrate processing region. The methods mayinclude contacting the aluminum halide material with the etchantprecursor. The methods may include removing the aluminum halidematerial.

In some embodiments, the halogen-containing precursor may include atransition metal, and the etchant precursor may be or include achlorine-containing precursor. The halogen-containing precursor mayinclude tungsten or niobium. The aluminum-containing material may be orinclude aluminum oxide. The etching method may be a plasma-free etchingprocess. The etching method may be performed at a temperature greaterthan or about 300° C. The etching method may be performed at a pressuregreater than or about 0.1 Torr. The etching method may be performed at apressure less than or about 50 Torr. The methods may include apre-treatment performed prior to flowing the halogen-containingprecursor. The pre-treatment may include contacting the substrate with aplasma comprising one or more of oxygen, hydrogen, or nitrogen. Themethods may include a post-treatment performed subsequent the etchingmethod. The post-treatment may include contacting the substrate with aplasma comprising one or more of oxygen, hydrogen, or nitrogen.

Some embodiments of the present technology may encompass etchingmethods. The methods may include forming a plasma of a treatmentprecursor including one or more of oxygen, hydrogen, or nitrogen toproduce treatment plasma effluents. The methods may include flowing thetreatment plasma effluents into a substrate processing region of asemiconductor processing chamber. The methods may include contacting asubstrate housed in the substrate processing region with the treatmentplasma effluents. The substrate may define an exposed region of analuminum-containing material. The treatment plasma effluents may beconfigured to remove a residue from a surface of the aluminum-containingmaterial. The methods may include flowing a first halogen-containingmaterial into the substrate processing region of the semiconductorprocessing chamber. The methods may include contacting the substratewith the first halogen-containing material. The methods may includeflowing a second halogen-containing precursor into the substrateprocessing region of the semiconductor processing chamber. The methodsmay include removing the aluminum-containing material.

In some embodiments, the first halogen-containing material may includetungsten or niobium or plasma effluents of a fluorine-containingprecursor. The second halogen-containing precursor may be or includeboron trichloride. The methods may include halting the plasma formationprior to flowing the first halogen-containing material. The etchingmethod may be performed at a temperature greater than or about 300° C.The etching method may be performed at a pressure greater than or about0.1 Torr. The methods may include a post-treatment performed subsequentthe etching method. The post-treatment may include contacting thesubstrate with a plasma comprising one or more of oxygen, hydrogen, ornitrogen.

Some embodiments of the present technology may encompass etchingmethods. The methods may include flowing a fluorine-containing precursorinto a substrate processing region of a semiconductor processingchamber. The fluorine-containing precursor may be characterized by a gasdensity greater than or about 5 g/L. The methods may include contactinga substrate housed in the substrate processing region with thefluorine-containing precursor. The substrate may define an exposedregion of an aluminum-containing material. The methods may includeflowing a chlorine-containing precursor into the substrate processingregion of the semiconductor processing chamber. The methods may includecontacting the substrate with the chlorine-containing precursor. Themethods may include removing the aluminum-containing material. Themethods may include forming a plasma of a treatment precursor includingone or more of oxygen, hydrogen, or nitrogen to produce treatment plasmaeffluents. The methods may include contacting the substrate with thetreatment plasma effluents.

In some embodiments, the fluorine-containing precursor may includetungsten or niobium, and the chlorine-containing precursor may includeboron. The treatment plasma effluents may be configured to removeresidual tungsten or niobium from one or more of the substrate or thesemiconductor processing chamber. The etching method may be performed ata temperature greater than or about 300° C. and at a pressure greaterthan or about 0.1 Torr.

Such technology may provide numerous benefits over conventional systemsand techniques. For example, the processes may allow dry etching to beperformed that may protect features of the substrate. Additionally, theprocesses may selectively remove aluminum-containing films relative toother exposed materials on the substrate. These and other embodiments,along with many of their advantages and features, are described in moredetail in conjunction with the below description and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedtechnology may be realized by reference to the remaining portions of thespecification and the drawings.

FIG. 1 shows a top plan view of one embodiment of an exemplaryprocessing system according to some embodiments of the presenttechnology.

FIG. 2A shows a schematic cross-sectional view of an exemplaryprocessing chamber according to some embodiments of the presenttechnology.

FIG. 2B shows a detailed view of a portion of the processing chamberillustrated in FIG. 2A according to some embodiments of the presenttechnology.

FIG. 3 shows a bottom plan view of an exemplary showerhead according tosome embodiments of the present technology.

FIG. 4 shows exemplary operations in a method according to someembodiments of the present technology.

FIGS. 5A-5B show schematic cross-sectional views of materials etchedaccording to some embodiments of the present technology.

Several of the figures are included as schematics. It is to beunderstood that the figures are for illustrative purposes, and are notto be considered of scale unless specifically stated to be of scale.Additionally, as schematics, the figures are provided to aidcomprehension and may not include all aspects or information compared torealistic representations, and may include additional or exaggeratedmaterial for illustrative purposes.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a letter thatdistinguishes among the similar components. If only the first referencelabel is used in the specification, the description is applicable to anyone of the similar components having the same first reference labelirrespective of the letter.

DETAILED DESCRIPTION

Diluted acids may be used in many different semiconductor processes forcleaning substrates and removing materials from those substrates. Forexample, diluted hydrofluoric acid can be an effective etchant forsilicon oxide, aluminum oxide, and other materials, and may be used toremove these materials from substrate surfaces. After the etching orcleaning operation is complete, the acid may be dried from the wafer orsubstrate surface. Using dilute hydrofluoric acid (“DHF”) may be termeda “wet” etch, and the diluent is often water. Additional etchingprocesses may be used that utilize precursors delivered to thesubstrate. For example, plasma enhanced processes may also selectivelyetch materials by enhancing precursors through the plasma to perform adry etch.

Although wet etchants using aqueous solutions or water-based processesmay operate effectively for certain substrate structures, the water maypose challenges in a variety of conditions. For example, utilizing waterduring etch processes may cause issues when disposed on substratesincluding metal materials. For example, certain later fabricationprocesses, such as recessing gaps, removing oxide dielectric, or otherprocesses to remove oxygen-containing materials, may be performed afteran amount of metallization has been formed on a substrate. If water isutilized in some fashion during the etching, an electrolyte may beproduced, which when contacting the metal material, may cause galvaniccorrosion to occur between dissimilar metals, and the metal may becorroded or displaced in various processes. In addition, because of thesurface tension of the water diluent, pattern deformation and collapsemay occur with minute structures. The water-based material may also beincapable of penetrating some high aspect ratio features due to surfacetension effects.

Plasma etching may overcome the issues associated with water-basedetching, although additional issues may occur. For example, aluminumoxide and other aluminum-based dielectrics have been incorporated inmany semiconductor structures, and exhibit dielectric properties.Because of the dielectric nature, these aluminum materials do notreadily conduct electricity. Accordingly, when charged plasma speciesare flowed towards these materials, charge buildup may occur along thesurface of the aluminum-based dielectric. Once accumulation hassurpassed a threshold, the electrical voltage may cause breakdown, whichcan damage the aluminum material.

The present technology overcomes these issues by performing a dry etchprocess that may passivate a number of materials relative to a materialto be etched, and in some embodiments a process may be plasma freeduring the etching. By utilizing particular precursors that mayfacilitate halogen dissociation to provide etchant materials, an etchprocess may be performed that may protect the surrounding structures.Additionally, the materials and conditions used may allow improvedetching relative to conventional techniques.

Although the remaining disclosure will routinely identify specificetching processes utilizing the disclosed technology, it will be readilyunderstood that the systems and methods are equally applicable todeposition and cleaning processes as may occur in the describedchambers, as well as other etching technology including mid andback-end-of-line processing and other etching that may be performed witha variety of exposed materials that may be maintained or substantiallymaintained. Accordingly, the technology should not be considered to beso limited as for use with the exemplary etching processes or chambersalone. Moreover, although an exemplary chamber is described to providefoundation for the present technology, it is to be understood that thepresent technology can be applied to virtually any semiconductorprocessing chamber that may allow the operations described.

FIG. 1 shows a top plan view of one embodiment of a processing system100 of deposition, etching, baking, and curing chambers according toembodiments. In the figure, a pair of front opening unified pods (FOUPs)102 supply substrates of a variety of sizes that are received by roboticarms 104 and placed into a low pressure holding area 106 before beingplaced into one of the substrate processing chambers 108 a-f, positionedin tandem sections 109 a-c. A second robotic arm 110 may be used totransport the substrate wafers from the holding area 106 to thesubstrate processing chambers 108 a-f and back. Each substrateprocessing chamber 108 a-f, can be outfitted to perform a number ofsubstrate processing operations including the dry etch processesdescribed herein in addition to cyclical layer deposition (CLD), atomiclayer deposition (ALD), chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, orientation, and othersubstrate processes.

The substrate processing chambers 108 a-f may include one or more systemcomponents for depositing, annealing, curing and/or etching a dielectricfilm on the substrate wafer. In one configuration, two pairs of theprocessing chambers, e.g., 108 c-d and 108 e-f, may be used to depositdielectric material on the substrate, and the third pair of processingchambers, e.g., 108 a-b, may be used to etch the deposited dielectric.In another configuration, all three pairs of chambers, e.g., 108 a-f,may be configured to etch a dielectric film on the substrate. Any one ormore of the processes described may be carried out in chamber(s)separated from the fabrication system shown in different embodiments. Itwill be appreciated that additional configurations of deposition,etching, annealing, and curing chambers for dielectric films arecontemplated by system 100.

FIG. 2A shows a cross-sectional view of an exemplary process chambersystem 200 with partitioned plasma generation regions within theprocessing chamber. During film etching, e.g., titanium nitride,tantalum nitride, tungsten, silicon, polysilicon, silicon oxide, siliconnitride, silicon oxynitride, silicon oxycarbide, etc., a process gas maybe flowed into the first plasma region 215 through a gas inlet assembly205. A remote plasma system (RPS) 201 may optionally be included in thesystem, and may process a first gas which then travels through gas inletassembly 205. The inlet assembly 205 may include two or more distinctgas supply channels where the second channel (not shown) may bypass theRPS 201, if included.

A cooling plate 203, faceplate 217, ion suppressor 223, showerhead 225,and a pedestal 265 or substrate support, having a substrate 255 disposedthereon, are shown and may each be included according to embodiments.The pedestal 265 may have a heat exchange channel through which a heatexchange fluid flows to control the temperature of the substrate, whichmay be operated to heat and/or cool the substrate or wafer duringprocessing operations. The wafer support platter of the pedestal 265,which may include aluminum, ceramic, or a combination thereof, may alsobe resistively heated in order to achieve relatively high temperatures,such as from up to or about 100° C. to above or about 1100° C., using anembedded resistive heater element.

The faceplate 217 may be pyramidal, conical, or of another similarstructure with a narrow top portion expanding to a wide bottom portion.The faceplate 217 may additionally be flat as shown and include aplurality of through-channels used to distribute process gases. Plasmagenerating gases and/or plasma excited species, depending on use of theRPS 201, may pass through a plurality of holes, shown in FIG. 2B, infaceplate 217 for a more uniform delivery into the first plasma region215.

Exemplary configurations may include having the gas inlet assembly 205open into a gas supply region 258 partitioned from the first plasmaregion 215 by faceplate 217 so that the gases/species flow through theholes in the faceplate 217 into the first plasma region 215. Structuraland operational features may be selected to prevent significant backflowof plasma from the first plasma region 215 back into the supply region258, gas inlet assembly 205, and fluid supply system 210. The faceplate217, or a conductive top portion of the chamber, and showerhead 225 areshown with an insulating ring 220 located between the features, whichallows an AC potential to be applied to the faceplate 217 relative toshowerhead 225 and/or ion suppressor 223. The insulating ring 220 may bepositioned between the faceplate 217 and the showerhead 225 and/or ionsuppressor 223 enabling a capacitively coupled plasma (CCP) to be formedin the first plasma region. A baffle (not shown) may additionally belocated in the first plasma region 215, or otherwise coupled with gasinlet assembly 205, to affect the flow of fluid into the region throughgas inlet assembly 205.

The ion suppressor 223 may comprise a plate or other geometry thatdefines a plurality of apertures throughout the structure that areconfigured to suppress the migration of ionically-charged species out ofthe first plasma region 215 while allowing uncharged neutral or radicalspecies to pass through the ion suppressor 223 into an activated gasdelivery region between the suppressor and the showerhead. Inembodiments, the ion suppressor 223 may comprise a perforated plate witha variety of aperture configurations. These uncharged species mayinclude highly reactive species that are transported with less reactivecarrier gas through the apertures. As noted above, the migration ofionic species through the holes may be reduced, and in some instancescompletely suppressed. Controlling the amount of ionic species passingthrough the ion suppressor 223 may advantageously provide increasedcontrol over the gas mixture brought into contact with the underlyingwafer substrate, which in turn may increase control of the depositionand/or etch characteristics of the gas mixture. For example, adjustmentsin the ion concentration of the gas mixture can significantly alter itsetch selectivity, e.g., SiNx:SiOx etch ratios, Si:SiOx etch ratios, etc.In alternative embodiments in which deposition is performed, it can alsoshift the balance of conformal-to-flowable style depositions fordielectric materials.

The plurality of apertures in the ion suppressor 223 may be configuredto control the passage of the activated gas, i.e., the ionic, radical,and/or neutral species, through the ion suppressor 223. For example, theaspect ratio of the holes, or the hole diameter to length, and/or thegeometry of the holes may be controlled so that the flow ofionically-charged species in the activated gas passing through the ionsuppressor 223 is reduced. The holes in the ion suppressor 223 mayinclude a tapered portion that faces the plasma excitation region 215,and a cylindrical portion that faces the showerhead 225. The cylindricalportion may be shaped and dimensioned to control the flow of ionicspecies passing to the showerhead 225. An adjustable electrical bias mayalso be applied to the ion suppressor 223 as an additional means tocontrol the flow of ionic species through the suppressor.

The ion suppressor 223 may function to reduce or eliminate the amount ofionically charged species traveling from the plasma generation region tothe substrate. Uncharged neutral and radical species may still passthrough the openings in the ion suppressor to react with the substrate.It should be noted that the complete elimination of ionically chargedspecies in the reaction region surrounding the substrate may not beperformed in embodiments. In certain instances, ionic species areintended to reach the substrate in order to perform the etch and/ordeposition process. In these instances, the ion suppressor may help tocontrol the concentration of ionic species in the reaction region at alevel that assists the process.

Showerhead 225 in combination with ion suppressor 223 may allow a plasmapresent in first plasma region 215 to avoid directly exciting gases insubstrate processing region 233, while still allowing excited species totravel from chamber plasma region 215 into substrate processing region233. In this way, the chamber may be configured to prevent the plasmafrom contacting a substrate 255 being etched. This may advantageouslyprotect a variety of intricate structures and films patterned on thesubstrate, which may be damaged, dislocated, or otherwise warped ifdirectly contacted by a generated plasma. Additionally, when plasma isallowed to contact the substrate or approach the substrate level, therate at which oxide species etch may increase. Accordingly, if anexposed region of material is oxide, this material may be furtherprotected by maintaining the plasma remotely from the substrate.

The processing system may further include a power supply 240electrically coupled with the processing chamber to provide electricpower to the faceplate 217, ion suppressor 223, showerhead 225, and/orpedestal 265 to generate a plasma in the first plasma region 215 orprocessing region 233. The power supply may be configured to deliver anadjustable amount of power to the chamber depending on the processperformed. Such a configuration may allow for a tunable plasma to beused in the processes being performed. Unlike a remote plasma unit,which is often presented with on or off functionality, a tunable plasmamay be configured to deliver a specific amount of power to the plasmaregion 215. This in turn may allow development of particular plasmacharacteristics such that precursors may be dissociated in specific waysto enhance the etching profiles produced by these precursors.

A plasma may be ignited either in chamber plasma region 215 aboveshowerhead 225 or substrate processing region 233 below showerhead 225.Plasma may be present in chamber plasma region 215 to produce theradical precursors from an inflow of, for example, a fluorine-containingprecursor or other precursor. An AC voltage typically in the radiofrequency (RF) range may be applied between the conductive top portionof the processing chamber, such as faceplate 217, and showerhead 225and/or ion suppressor 223 to ignite a plasma in chamber plasma region215 during deposition. An RF power supply may generate a high RFfrequency of 13.56 MHz but may also generate other frequencies alone orin combination with the 13.56 MHz frequency.

FIG. 2B shows a detailed view 253 of the features affecting theprocessing gas distribution through faceplate 217. As shown in FIGS. 2Aand 2B, faceplate 217, cooling plate 203, and gas inlet assembly 205intersect to define a gas supply region 258 into which process gases maybe delivered from gas inlet 205. The gases may fill the gas supplyregion 258 and flow to first plasma region 215 through apertures 259 infaceplate 217. The apertures 259 may be configured to direct flow in asubstantially unidirectional manner such that process gases may flowinto processing region 233, but may be partially or fully prevented frombackflow into the gas supply region 258 after traversing the faceplate217.

The gas distribution assemblies such as showerhead 225 for use in theprocessing chamber section 200 may be referred to as dual channelshowerheads (DCSH) and are additionally detailed in the embodimentsdescribed in FIG. 3. The dual channel showerhead may provide for etchingprocesses that allow for separation of etchants outside of theprocessing region 233 to provide limited interaction with chambercomponents and each other prior to being delivered into the processingregion.

The showerhead 225 may comprise an upper plate 214 and a lower plate216. The plates may be coupled with one another to define a volume 218between the plates. The coupling of the plates may be so as to providefirst fluid channels 219 through the upper and lower plates, and secondfluid channels 221 through the lower plate 216. The formed channels maybe configured to provide fluid access from the volume 218 through thelower plate 216 via second fluid channels 221 alone, and the first fluidchannels 219 may be fluidly isolated from the volume 218 between theplates and the second fluid channels 221. The volume 218 may be fluidlyaccessible through a side of the showerhead 225.

FIG. 3 is a bottom view of a showerhead 325 for use with a processingchamber according to embodiments. Showerhead 325 may correspond with theshowerhead 225 shown in FIG. 2A. Through-holes 365, which show a view offirst fluid channels 219, may have a plurality of shapes andconfigurations in order to control and affect the flow of precursorsthrough the showerhead 225. Small holes 375, which show a view of secondfluid channels 221, may be distributed substantially evenly over thesurface of the showerhead, even amongst the through-holes 365, and mayhelp to provide more even mixing of the precursors as they exit theshowerhead than other configurations.

The chamber discussed previously may be used in performing exemplarymethods including etching methods. Turning to FIG. 4 is shown exemplaryoperations in a method 400 according to embodiments of the presenttechnology. Method 400 may include one or more operations prior to theinitiation of the method, including front end processing, deposition,gate formation, etching, polishing, cleaning, or any other operationsthat may be performed prior to the described operations. The method mayinclude a number of optional operations, which may or may not bespecifically associated with some embodiments of methods according tothe present technology. For example, many of the operations aredescribed in order to provide a broader scope of the processesperformed, but are not critical to the technology, or may be performedby alternative methodology as will be discussed further below. Method400 may describe operations shown schematically in FIGS. 5A-5B, theillustrations of which will be described in conjunction with theoperations of method 400. It is to be understood that the figuresillustrate only partial schematic views, and a substrate may contain anynumber of additional materials and features having a variety ofcharacteristics and aspects as illustrated in the figures.

Method 400 may or may not involve optional operations to develop thesemiconductor structure to a particular fabrication operation. It is tobe understood that method 400 may be performed on any number ofsemiconductor structures or substrates 505, as illustrated in FIG. 5A,including exemplary structures on which an oxide removal operation maybe performed. Exemplary semiconductor structures may include a trench,via, or other recessed features that may include one or more exposedmaterials. For example, an exemplary substrate may contain silicon orsome other semiconductor substrate material as well as interlayerdielectric materials through which a recess, trench, via, or isolationstructure may be formed. Exposed materials at any time during the etchprocess may be or include metal materials such as for a gate, adielectric material, a contact material, a transistor material, or anyother material that may be used in semiconductor processes. In someembodiments exemplary substrates may include an aluminum-containingmaterial 515, such as aluminum oxide, or some other aluminum-containingdielectric. The aluminum-containing material may be exposed relative toone or more other materials 510 including metals, other dielectricsincluding silicon oxide or nitride, or any of a number of othersemiconductor materials relative to which the aluminum-containingmaterial is to be removed, such as a nitride of titanium, tantalum, orother materials.

It is to be understood that the noted structure is not intended to belimiting, and any of a variety of other semiconductor structuresincluding aluminum-containing materials are similarly encompassed. Otherexemplary structures may include two-dimensional and three-dimensionalstructures common in semiconductor manufacturing, and within which analuminum-containing material such as aluminum oxide is to be removedrelative to one or more other materials, as the present technology mayselectively remove aluminum-containing materials relative to otherexposed materials, such as silicon-containing materials, and any of theother materials discussed elsewhere. Additionally, although ahigh-aspect-ratio structure may benefit from the present technology, thetechnology may be equally applicable to lower aspect ratios and anyother structures.

For example, layers of material according to the present technology maybe characterized by any aspect ratios or the height-to-width ratio ofthe structure, although in some embodiments the materials may becharacterized by larger aspect ratios, which may not allow sufficientetching utilizing conventional technology or methodology. For example,in some embodiments the aspect ratio of any layer of an exemplarystructure may be greater than or about 10:1, greater than or about 20:1,greater than or about 30:1, greater than or about 40:1, greater than orabout 50:1, or greater. Additionally, each layer may be characterized bya reduced width or thickness less than or about 100 nm, less than orabout 80 nm, less than or about 60 nm, less than or about 50 nm, lessthan or about 40 nm, less than or about 30 nm, less than or about 20 nm,less than or about 10 nm, less than or about 5 nm, less than or about 1nm, or less, including any fraction of any of the stated numbers, suchas 20.5 nm, 1.5 nm, etc. This combination of high aspect ratios andminimal thicknesses may frustrate many conventional etching operations,or require substantially longer etch times to remove a layer, along avertical or horizontal distance through a confined width. Moreover,damage to or removal of other exposed layers may occur with conventionaltechnologies as well.

Method 400 may be performed to remove an exposed aluminum-containingmaterial in embodiments, although any number of oxide oraluminum-containing materials may be removed in any number of structuresin embodiments of the present technology. The methods may includespecific operations for the removal of aluminum-containing materials,and may include one or more optional operations to prepare or treat thealuminum-containing materials. For example, an exemplary substratestructure may have previous processing residues on a film to be removed,such as aluminum oxide. For example, residual photoresist or byproductsfrom previous processing may reside on the aluminum oxide layer. Thesematerials may prevent access to the aluminum oxide, or may interact withetchants differently than a clean aluminum oxide surface, which mayfrustrate one or more aspects of the etching. Accordingly, in someembodiments an optional pre-treatment of the aluminum-containing film ormaterial may occur at optional operation 405. Exemplary pre-treatmentoperations may include a thermal treatment, wet treatment, or plasmatreatment, for example, which may be performed in chamber 200 as well asany number of chambers that may be included on system 100 describedabove.

In one exemplary plasma treatment, a remote or local plasma may bedeveloped from a precursor intended to interact with residues in one ormore ways. For example, utilizing chambers such as chamber 200 describedabove, either a remote or local plasma may be produced from one or moreprecursors. For example, an oxygen-containing precursor, ahydrogen-containing precursor, a nitrogen-containing precursor, ahelium-containing precursor, or some other precursor may be flowed intoa remote plasma region or into the processing region, where a plasma maybe struck. The plasma effluents may be flowed to the substrate, and maycontact the residue material. The plasma process may be either physicalor chemical depending on the material to be removed to expose thealuminum-containing material. For example, plasma effluents may beflowed to contact and physically remove the residue, such as by asputtering operation, or the precursors may be flowed to interact withthe residues to produce volatile byproducts that may be removed from thechamber.

Exemplary precursors used in the pre-treatment may be or includehydrogen, a hydrocarbon, water vapor, an alcohol, hydrogen peroxide, orother materials that may include hydrogen as would be understood by theskilled artisan. Exemplary oxygen-containing precursors may includemolecular oxygen, ozone, nitrous oxide, nitric oxide, or otheroxygen-containing materials. Nitrogen gas may also be used, or acombination precursor having one or more of hydrogen, oxygen, and/ornitrogen may be utilized to remove particular residues. Once the residueor byproducts have been removed, a clean aluminum-oxide surface may beexposed for etching.

Method 400 may include flowing a halogen-containing precursor, includinga first halogen-containing precursor, into the substrate processingregion of a semiconductor processing chamber housing the describedsubstrate, or some other substrate, at operation 410. Thehalogen-containing precursor may be flowed through a remote plasmaregion of the processing chamber, such as region 215 described above,although in some embodiments method 400 may not utilize plasma effluentsduring the etching operations. For example, method 400 may flow afluorine-containing or other halogen-containing precursor to thesubstrate without exposing the precursor to a plasma, and may performthe removal of the aluminum-containing material without production ofplasma effluents. In some embodiments the halogen-containing precursormay be plasma enhanced, which may occur in a remote plasma region toprotect materials on the substrate from contact with plasma effluents.The halogen-containing precursor may contact a semiconductor substrateincluding an exposed aluminum-containing material, and may produce afluorinated material, such as aluminum fluoride or an aluminum halidematerial, which may remain on the semiconductor substrate. Thehalogen-containing precursor may donate one or more fluorine atoms,while accepting one or more oxygen atoms in some embodiments. Somehalogen-containing precursors, such as plasma enhanced precursors, mayprovide fluorine radicals, while other plasma radicals may accept oxygenfrom the film.

Subsequent the fluorination operation, an etchant precursor may beflowed into the processing region at operation 415. In some embodiments,the etchant precursor may be a second halogen-containing precursor, andmay include the same or a different halogen as the firsthalogen-containing precursor. The etchant precursor may furthersubstitute to produce an aluminum byproduct that may be volatile underprocessing conditions, and may be evolved from the substrate.Accordingly, the etchant precursor may etch or remove the aluminummaterial at operation 420, as shown in FIG. 5B.

As noted above, the present technology may be performed without plasmadevelopment during the etching operations 410-420. By utilizingparticular precursors, and performing the etching within certain processconditions, a plasma-free removal may be performed, and the removal mayalso be a dry etch. Accordingly, techniques according to aspects of thepresent technology may be performed to remove aluminum oxide from narrowfeatures, as well as high aspect ratio features, and thin dimensionsthat may otherwise be unsuitable for wet etching. An optional operationmay be performed to clear the substrate or chamber of residues and mayinclude a post-treatment at optional operation 425. The post-treatmentmay include similar operations as the pre-treatment, and may include anyof the precursors or operations discussed above for the pre-treatment.The post-treatment may clear residual transition metal from thesubstrate or chamber in some embodiments. It is to be understood thatalthough the pre-treatment and/or post-treatment operations may includeplasma generation and plasma effluent delivery to the substrate, plasmamay not be formed during the etching operations. For example, in someembodiments no plasma may be generated while the halogen-containingprecursor or precursors are being delivered into the processing chamber.Additionally, in some embodiments, the etching precursors may behydrogen-free in some embodiments, and the etching method may notinclude hydrogen-containing precursors during the etching, althoughhydrogen-containing precursors may be used during either or both of theoptional pre-treatment or post-treatment operations.

The precursors during each of the two-step operation may includehalogen-containing precursors, and may include one or more of fluorineor chlorine in some embodiments. The specific precursors may be based onbonding or stability of the precursors. For example, in some embodimentsthe first halogen-containing precursor may include a transition metaland/or may be characterized by a particular gas density. The transitionmetal may include any transition metal which may be capable of bondingwith halogens, and which may dissociate under operating conditions asdiscussed below. Exemplary transition metals may include tungsten,niobium, or any other materials, and may includetransition-metal-and-halogen-containing precursors characterized by agas density greater than or about 3 g/L, and may be characterized by agas density of greater than or about 4 g/L, greater than or about 5 g/L,greater than or about 6 g/L, greater than or about 7 g/L, greater thanor about 8 g/L, greater than or about 9 g/L, greater than or about 10g/L, greater than or about 11 g/L, greater than or about 12 g/L, greaterthan or about 13 g/L, or higher.

These precursors may be characterized by relatively high thermal andchemical stability because of the nature of bonding between the heavymetal and the halogen. The precursors may also be characterized by atransition metal characterized by relatively low resistivity, which mayfurther facilitate bonding stability at lower temperatures, and faciledissociation at elevated temperatures. Accordingly, the materials may becharacterized by a resistivity of less than or about 50 μΩ·cm, and maybe characterized by a resistivity of less than or about 40 μΩ·cm, lessthan or about 30 μΩ·cm, less than or about 20 μΩ·cm, less than or about15 μΩ·cm, less than or about 10 μΩ·cm, less than or about 5 μΩ·cm, orless. The precursors may also include any number of carrier gases, whichmay include nitrogen, helium, argon, or other noble, inert, or usefulprecursors.

Some exemplary precursors that may include the stated characteristicsmay include tungsten hexafluoride, tungsten pentachloride, niobiumtetrachloride, or other transition metal halides, as well as otherhalides including hydrogen fluoride, nitrogen trifluoride, or anyorganofluoride. The precursors may also be flown together in a varietyof combinations. In some embodiments, nitrogen trifluoride, or someother fluorine-containing precursor may be delivered to a remote plasmaregion with hydrogen and plasma enhanced to produce a fluorinatedsurface of aluminum in the first operation. Etchant precursors accordingto some embodiments of the present technology may specifically includeheavy metal halides, which may be characterized by stability atatmospheric conditions, with relatively facile dissociation at increasedtemperature. For example, exemplary precursors may be characterized byrelatively weak bonding at elevated temperatures, which may allowcontrolled exposure of aluminum oxide to halogen etchants.

As a non-limiting example, tungsten hexafluoride may readily donate afluorine atom or two at elevated temperatures, and accept an oxygenatom, such as from the aluminum oxide, and be maintained in a gas phase.Accordingly, tungsten oxide fluorides may be developed as reactionbyproducts, which may be gas molecules and may be pumped or removed fromthe processing chamber. Because aluminum fluoride may not be volatile, achlorine-containing precursor, bromine-containing precursor, oriodine-containing precursor, any of which may include boron, titanium,tin, molybdenum, tungsten, or niobium, may be used to donate chlorine,bromine, or iodine, and accept fluorine at the same temperatures. Whilechlorine, bromine, or iodine may not readily be donated relative toaluminum oxide, the materials may be donated to aluminum fluoride whilethe etchant precursor may accept the fluorine producing two volatilecomponents, including aluminum chloride, which may be exhausted from theprocessing chamber. Accordingly, the process may remove aluminum oxideunder processing conditions configured to exchange fluorine and oxygenbetween the etchant and the exposed surface, followed by an exchange offluorine for chlorine, and produce volatile aluminum byproducts, andmaintain a majority of the tungsten and etchant precursor in vapor form.Accordingly, tungsten and other heavy metals similarly encompassed bythe present technology may have limited or essentially no interactionwith the process, while delivering halogens to the materials to beetched. Because of the controlled delivery, tungsten oxide and othermetal halides may not etch or may minimally interact with other exposedsurfaces, while readily removing aluminum oxide, which may produceenhanced selectivity over conventional techniques.

Processing conditions may impact and facilitate etching according to thepresent technology. Because the etch reaction may proceed based onthermal dissociation of halogen from the transition metals, thetemperatures may be at least partially dependent on the particularhalogen and/or transition metal of the precursor in order to initiatedissociation. As illustrated, as temperature increases above or about300° C., etching begins to occur or increase, which may indicatedissociation of the precursor, and/or activation of the reaction withaluminum oxide. As temperature continues to increase, dissociation maybe further facilitated as may the reaction with aluminum oxide.

Accordingly, in some embodiments of the present technology, etchingmethods may be performed at substrate, pedestal, and/or chambertemperatures above or about 300° C., and may be performed attemperatures above or about 350° C., above or about 400° C., above orabout 450° C., above or about 500° C., or higher. The temperature mayalso be maintained at any temperature within these ranges, withinsmaller ranges encompassed by these ranges, or between any of theseranges. In some embodiments the method may be performed on substratesthat may have a number of produced features, which may produce a thermalbudget. Accordingly, in some embodiments, the methods may be performedat temperatures below or about 800° C., and may be performed attemperatures below or about 750° C., below or about 700° C., below orabout 650° C., below or about 600° C., below or about 550° C., below orabout 500° C., or lower.

The pressure within the chamber may also affect the operations performedas well as affect at what temperature the halogen may dissociate fromthe transition metal. Accordingly, in some embodiments the pressure maybe maintained below about 50 Torr, below or about 40 Torr, below orabout 30 Torr, below or about 25 Torr, below or about 20 Torr, below orabout 15 Torr, below or about 10 Torr, below or about 9 Torr, below orabout 8 Torr, below or about 7 Torr, below or about 6 Torr, below orabout 5 Torr, below or about 4 Torr, below or about 3 Torr, below orabout 2 Torr, below or about 1 Torr, below or about 0.1 Torr, or less.The pressure may also be maintained at any pressure within these ranges,within smaller ranges encompassed by these ranges, or between any ofthese ranges. In some embodiments, etch amount may be facilitated andmay initiate as pressure increases above about 1 Torr. Additionally, aspressure continues to increase, etching may improve up to a point beforebeginning to reduce, and eventually cease as pressure continues toincrease.

Without being bound to any particular theory, pressure within thechamber may affect processing with precursors described above. At lowpressures, flow across a substrate may be reduced, and dissociation maysimilarly be reduced. As pressure increases, interactions between theetchant precursor and the substrate may increase, which may increasereactions and etch rates. However, as pressure continues to increase,recombination of the dissociated halogen atoms with the heavy metal basemay increase due to the relative stability of the molecules. Thus, theprecursors may effectively be pumped back out of the chamber withoutreacting with the substrate. Additionally, interactions with thealuminum oxide surface may be suppressed as pressure continues toincrease, or byproduct aluminum fluoride may be reintroduced to the filmbeing etched, further limiting removal. Accordingly, in someembodiments, pressure within the processing chamber may be maintainedbelow or about 10 Torr in some embodiments.

Flow rates of the halogen-containing precursor may be tuned, includingin situ, to control the etch process. For example, a flow rate of thehalogen-containing precursor may be reduced, maintained, or increasedduring the removal operations. By increasing the flow rate of thehalogen-containing precursor, etch rates may be increased up to a pointof saturation. During any of the operations of method 400, the flow rateof the fluorine-containing precursor may be between about 5 sccm andabout 1,000 sccm. Additionally, the flow rate of the halogen-containingprecursor may be maintained below or about 900 sccm, below or about 800sccm, below or about 700 sccm, below or about 600 sccm, below or about500 sccm, below or about 400 sccm, below or about 300 sccm, below orabout 200 sccm, below or about 100 sccm, or less. The flow rate may alsobe between any of these stated flow rates, or within smaller rangesencompassed by any of these numbers.

Adding further control to the etch process, the halogen-containingprecursor may be pulsed in some embodiments, and may be deliveredthroughout the etch process either continually or in a series of pulses,which may be consistent or varying over time. The pulsed delivery may becharacterized by a first period of time during which thehalogen-containing precursor is flowed, and a second period of timeduring which the halogen-containing precursor is paused or halted. Thetime periods for any pulsing operation may be similar or different fromone another with either time period being longer. In embodiments eitherperiod of time or a continuous flow of precursor may be performed for atime period greater than or about 1 second, and may be greater than orabout 2 seconds, greater than or about 3 seconds, greater than or about4 seconds, greater than or about 5 seconds, greater than or about 6seconds, greater than or about 7 seconds, greater than or about 8seconds, greater than or about 9 seconds, greater than or about 10seconds, greater than or about 11 seconds, greater than or about 12seconds, greater than or about 13 seconds, greater than or about 14seconds, greater than or about 15 seconds, greater than or about 20seconds, greater than or about 30 seconds, greater than or about 45seconds, greater than or about 60 seconds, or longer. The times may alsobe any smaller range encompassed by any of these ranges. In someembodiments as delivery of the precursor occurs for longer periods oftime, etch rate may increase.

By performing operations according to embodiments of the presenttechnology, aluminum oxide or other aluminum-containing materials may beetched selectively relative to other materials, including other oxides.For example, the present technology may selectively etch aluminum oxiderelative to exposed regions of metals, dielectrics includingsilicon-containing materials including silicon oxide, or othermaterials. Embodiments of the present technology may etch aluminum oxiderelative to silicon oxide or any of the other materials at a rate of atleast about 20:1, and may etch aluminum oxide relative to silicon oxideor other materials noted at a selectivity greater than or about 25:1,greater than or about 30:1, greater than or about 50:1, greater than orabout 100:1, greater than or about 150:1, greater than or about 200:1,greater than or about 250:1, greater than or about 300:1, greater thanor about 350:1, greater than or about 400:1, greater than or about450:1, greater than or about 500:1, or more. For example, etchingperformed according to some embodiments of the present technology mayetch aluminum oxide while substantially or essentially maintainingsilicon oxide or other materials, such as nitrides of silicon, titanium,tantalum, or other materials.

Selectivity may be based in part on precursors used, and the ability todissociate at more controlled temperature ranges. For example,conventional precursors, including nitrogen trifluoride, may not asreadily dissociate at temperatures below or about 500° C. at operatingpressures, and may also be characterized by a slower reaction rate withthe material to be removed, which may increase the exposure time ofother materials on a substrate, and which may increase removal of thesematerials. Accordingly, conventional dry etchants may be incapable ofproducing etch selectivities of embodiments of the present technology.Similarly, because wet etchants readily remove silicon oxide, wetetchants may also be incapable of etching selectively at ratescomparable to embodiments of the present technology.

The previously discussed methods may allow the removal ofaluminum-containing materials relative to a number of other exposedmaterials. By utilizing transition metals as described previously,improved etching of aluminum oxide may be performed, which may bothincrease selectivity over conventional techniques, as well as improveetching access in small pitch features.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious embodiments of the present technology. It will be apparent toone skilled in the art, however, that certain embodiments may bepracticed without some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theembodiments. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent technology. Accordingly, the above description should not betaken as limiting the scope of the technology. Additionally, methods orprocesses may be described as sequential or in steps, but it is to beunderstood that the operations may be performed concurrently, or indifferent orders than listed.

Where a range of values is provided, it is understood that eachintervening value, to the smallest fraction of the unit of the lowerlimit, unless the context clearly dictates otherwise, between the upperand lower limits of that range is also specifically disclosed. Anynarrower range between any stated values or unstated intervening valuesin a stated range and any other stated or intervening value in thatstated range is encompassed. The upper and lower limits of those smallerranges may independently be included or excluded in the range, and eachrange where either, neither, or both limits are included in the smallerranges is also encompassed within the technology, subject to anyspecifically excluded limit in the stated range. Where the stated rangeincludes one or both of the limits, ranges excluding either or both ofthose included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “a precursor” includes aplurality of such precursors, and reference to “the layer” includesreference to one or more layers and equivalents thereof known to thoseskilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”,“include(s)”, and “including”, when used in this specification and inthe following claims, are intended to specify the presence of statedfeatures, integers, components, or operations, but they do not precludethe presence or addition of one or more other features, integers,components, operations, acts, or groups.

The invention claimed is:
 1. An etching method comprising: flowing ahalogen-containing precursor into a substrate processing region of asemiconductor processing chamber, wherein the halogen-containingprecursor is characterized by a gas density greater than or about 5 g/L;contacting a substrate housed in the substrate processing region withthe halogen-containing precursor, wherein the substrate defines anexposed region of an aluminum-containing material, and wherein thecontacting produces an aluminum halide material; flowing an etchantprecursor into the substrate processing region; contacting the aluminumhalide material with the etchant precursor; and removing the aluminumhalide material.
 2. The etching method of claim 1, wherein thehalogen-containing precursor comprises a transition metal, and whereinthe etchant precursor comprises a chlorine-containing precursor.
 3. Theetching method of claim 2, wherein the halogen-containing precursorcomprises tungsten or niobium.
 4. The etching method of claim 1, whereinthe aluminum-containing material comprises aluminum oxide.
 5. Theetching method of claim 1, wherein the etching method comprises aplasma-free etching process.
 6. The etching method of claim 1, whereinthe etching method is performed at a temperature greater than or about300° C.
 7. The etching method of claim 1, wherein the etching method isperformed at a pressure greater than or about 0.1 Torr.
 8. The etchingmethod of claim 7, wherein the etching method is performed at a pressureless than or about 50 Torr.
 9. The etching method claim 1, furthercomprising a pre-treatment performed prior to flowing thehalogen-containing precursor, wherein the pre-treatment comprisescontacting the substrate with a plasma comprising one or more of oxygen,hydrogen, or nitrogen.
 10. The etching method claim 1, furthercomprising a post-treatment performed subsequent the etching method,wherein the post-treatment comprises contacting the substrate with aplasma comprising one or more of oxygen, hydrogen, or nitrogen.
 11. Anetching method comprising: forming a plasma of a treatment precursorcomprising one or more of oxygen, hydrogen, or nitrogen to producetreatment plasma effluents; flowing the treatment plasma effluents intoa substrate processing region of a semiconductor processing chamber;contacting a substrate housed in the substrate processing region withthe treatment plasma effluents, wherein the substrate defines an exposedregion of an aluminum-containing material, and wherein the treatmentplasma effluents are configured to remove a residue from a surface ofthe aluminum-containing material; flowing a first halogen-containingmaterial into the substrate processing region of the semiconductorprocessing chamber; contacting the substrate with the firsthalogen-containing material; flowing a second halogen-containingprecursor into the substrate processing region of the semiconductorprocessing chamber; and removing the aluminum-containing material. 12.The etching method of claim 11, wherein the first halogen-containingmaterial comprises tungsten or niobium or plasma effluents of afluorine-containing precursor, and wherein the second halogen-containingprecursor comprises boron trichloride.
 13. The etching method of claim11, further comprising halting the plasma formation prior to flowing thefirst halogen-containing material.
 14. The etching method of claim 11,wherein the etching method is performed at a temperature greater than orabout 300° C.
 15. The etching method of claim 11, wherein the etchingmethod is performed at a pressure greater than or about 0.1 Torr. 16.The etching method of claim 11, further comprising a post-treatmentperformed subsequent the etching method, wherein the post-treatmentcomprises contacting the substrate with a plasma comprising one or moreof oxygen, hydrogen, or nitrogen.
 17. An etching method comprising:flowing a fluorine-containing precursor into a substrate processingregion of a semiconductor processing chamber, wherein thefluorine-containing precursor is characterized by a gas density greaterthan or about 5 g/L; contacting a substrate housed in the substrateprocessing region with the fluorine-containing precursor, wherein thesubstrate defines an exposed region of an aluminum-containing material;flowing a chlorine-containing precursor into the substrate processingregion of the semiconductor processing chamber; contacting the substratewith the chlorine-containing precursor; removing the aluminum-containingmaterial; forming a plasma of a treatment precursor comprising one ormore of oxygen, hydrogen, or nitrogen to produce treatment plasmaeffluents; and contacting the substrate with the treatment plasmaeffluents.
 18. The etching method of claim 17, wherein thefluorine-containing precursor comprises tungsten or niobium, and whereinthe chlorine-containing precursor comprises boron.
 19. The etchingmethod of claim 18, wherein the treatment plasma effluents areconfigured to remove residual tungsten or niobium from one or more ofthe substrate or the semiconductor processing chamber.
 20. The etchingmethod of claim 17, wherein the etching method is performed at atemperature greater than or about 300° C. and at a pressure greater thanor about 0.1 Torr.